Abstract

This article presents results on CrCuN nanocomposite coatings grown by physical vapor deposition. The immiscibility of Cr (containing a supersaturation of nitrogen) and Cu offers the potential of depositing a predominantly metallic (and therefore tough) nanocomposite, composed of small Cr(N) metallic and/or {beta}-Cr{sub 2}N ceramic grains interdispersed in a (minority) Cu matrix. A range of CrCuN compositions have been deposited using a hot-filament enhanced unbalanced magnetron sputtering system. The stoichiometry and nanostructure have been studied by x-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, and x-ray diffraction. Hardness, wear resistance, and impact resistance have been determined by nanoindentation, reciprocating-sliding, and ball-on-plate high-cycle impact. Evolution of the nanostructure as a function of composition and correlations of the nanostructure and mechanical properties of the CrCuN coatings are discussed. A nanostructure comprised of 1-3 nm {alpha}-Cr(N) and {beta}-Cr{sub 2}N grains separated by intergranular regions of Cu gives rise to a coating with significantly enhanced resistance to impact wear.

Monolithic TiN coatings deposited onto cemented carbide cutting tool inserts coated by chemical vapor deposition (CVD) or physical vapor deposition (PVD) methods, respectively, were subjected to pulsed intense electron beam treatments in the energy range 3 to 5 J{center{underscore}dot}cm{sup {minus}2}. The temperature profiles for this rapid thermal processing (RTP) covered the range between fusion of the cobalt binder in the carbide to surface fusion of the TiN coatings. The treatment caused extensive cracking in all coatings, removed the atomic level defects, vacancies and dislocations, and the residual stress in the PVD coatings, but caused little change in the CVD coatings.more » There was some nitrogen loss very close to the surface but no change in the stoichiometry of the bulk of the nitride. In contrast, no changes were found in the carbide substrate below the PVD coatings, but microscopic changes were found immediately below the surface in the carbide under the CVD coatings. Steel turning tests suggest that treatment of the PVD coatings at the lowest power used, 3 J{center{underscore}dot}cm{sup {minus}2}, reduced the flank wear by a factor of 2 but had no effect on any of the CVD coatings.« less

Deposition of composite materials as thin film by electron beam physical vapor deposition technique (EB-PVD) still remains as a challenge. Here, the authors report the deposition of NiO-CeO{sub 2} (30/70 wt. %) composites on quartz substrate by EB-PVD. Two NiO-CeO{sub 2} nanocomposite targets—one as green compact and the other after sintering at 1250 °C—were used for the deposition. Though the targets varied with respect to physical properties such as crystallite size (11–45 nm) and relative density (44% and 96%), the resultant thin films exhibited a mean crystallite size in the range of 20–25 nm underlining the role of physical nature of deposition. In spitemore » of the crystalline nature of the targets and similar elemental concentration, a transformation from amorphous to crystalline structure was observed in thin films on using sintered target. Postannealing of the as deposited film at 800 °C resulted in a polycrystalline structure consisting of CeO{sub 2} and NiO. Deposition using pure CeO{sub 2} or NiO as target resulted in the preferential orientation toward (111) and (200) planes, respectively, showing the influence of adatoms on the evaporation and growth process of NiO-CeO{sub 2} composite. The results demonstrate the influence of electron beam gun power on the adatom energy for the growth process of composite oxide thin films.« less

Ti-Si-N-O nanocomposite coatings with different contents of oxygen were deposited by a combined dc/rf reactive unbalanced magnetron sputtering process in an Ar+N{sub 2}+O{sub 2} mixture atmosphere. The composition, structure, mechanical, and tribological properties of the as-deposited coatings were analyzed by energy dispersive analysis of x-rays, x-ray diffraction (XRD), nanoindentation, and pin-on-disk tribometer experiments, respectively. It was found that in the range of lower oxygen content with atomic ratio of O/N{<=}0.72, the tribological properties of the Ti-Si-N-O coatings are evidently improved, in comparison with the coating without oxygen incorporation. At O/N=0.72, the friction coefficient and wear rate of the as-deposited coatingsmore » are reduced to 20% and 45%, respectively. Meanwhile, however, their hardness was not reduced, but, on the contrary, slightly increased. With increasing oxygen content further to O/N{>=}0.72, coating hardness decreased significantly. The friction coefficient of the as-deposited coatings decreased monotonously with the increase of oxygen content in the whole composition range investigated. The wear rate of the coatings exhibited a minimum value at around O/N=0.72. In the lower range of O/N, wear rate decreased significantly due to the lubricant effect of oxygen incorporation, while in the higher range of O/N, wear rate increased gradually due to the weakening of coating hardness. XRD patterns revealed that the as-deposited coatings were mainly crystallized in cubic TiN phase, accompanied with minority of rutile structure titania in the case of higher oxygen incorporation.« less

Hexagonal boron nitride (h-BN) and tungsten carbide cobalt (WC–Co) were added to nickel aluminum alloy (Ni–Al) and deposited as plasma sprayed coatings to improve their tribological properties. The microstructure of the coatings was analyzed using a scanning electron microscope (SEM). Following wear test, the worn surface morphologies of the coatings were analyzed using a SEM to identify their fracture modes. The results of this study demonstrate that the addition of h-BN and WC–Co improved the properties of the coatings. Ni–Al/h-BN/WC–Co coatings with high hardness and favorable lubrication properties were deposited. - Highlights: • We mixed Ni–Al, h-BN and WC–Co powdersmore » and deposited them as composite coatings. • Adding WC–Co was found to increase the hardness and reduce the wear volume loss. • Adding h-BN was found to decrease the hardness and reduce the friction coefficient. • This composite coating was shown to have improved wear properties at 850 °C.« less